Dressing mechanism



Feb. 16, 1943.A A. STEWART Y DRESSING MEQHANISM Filed June 3, 1940 3 Sheets-Sheet l mm. R bq. ww uw :inventor SNN? Feb. 16, 1943. A. L. rSTEWART 2,311,262.

DRESSING MECHANISM Filed June 3, 1940 Y 3 Sheets-Sheet 2 nventor 9m-Hak L. STEM/a? i E mi@ attorney Feb. 16, 1943. A STEWART 2,311,262

- DRESSING MECHANISM Filed June s, 1940 :s sheets-sheet s Patented Feb. 16, 1943 STTS PATNT OFFICE of New York application .time 3, 1940', serial' No. 338562 (ci. 12s-11) 2 Claims.

The present invention relates to dressing mechanisms and particularly to mechanisms for dressing the side surfaces of grinding wheels such as are employed in the grinding of longitudinally curved tooth bevel and hypoid gears.

One object of the present invention is to provide a dressing mechanism which may be adapted readily to the dressing of any desired prole shape onra grinding wheel.

A further object of the invention is to provide a dressing mechanism that may be used to dress the greater portion of the height of an active side surface of a grinding wheel to one pressure angle and to dress the remaining portion of the height of said side surface of the wheel to either a greater or a lesser pressure angle. Y

Other objects of the invention will be apparent hereinafter from the specication and from the recital of the appended claims.

The present invention has wide application. It may be used for dressing grinding wheels of any desired shape. One particular use of the mechanism is in the dressing of annular `grinding wheels such as are used for grinding in a generating operation the teeth of longitudinally'curved tooth bevel and hyp'oid gears. Such a wheel ordinarily has opposite sides dressed to positive pressure angles. The opposite sides of such a wheel converge, therefore, toward the tip of the wheel withthe result that the wheel is of relatively thin section near its tip. It has been found that because of this thin section,y the wheel may deect away from the gear tooth being ground, particularly when pinions are being ground, since only one side of a pinion tooth is ordinarily ground at a time. When this deflection occurs, the wheel does not remove `an even amount of stock over the full height of the pinion tooth and more stock than is desired may be left near the roots ofthe teeth. During the generating roll, moreover, the wheel may wear away faster near its tip than over the rest of its height. This, too, tends to cause the wheel to leave on more stock than desired near the roots of the teeth of the pinion's. The excess amount of stock left near the roots tends to produce an interference when the pinion is run with its mate gear and the pair may, therefore, be noisy. If the wheelis dressed, however, with smaller pressure angles adjacent its tip than along the rest of its height, the wheel will be more rigid near its tipv and, moreover, the smaller pressure anglerportion of the wheel surface will tend to relieve the tooth surface of the pinionunear'its, root and this tendency will offset any tendency of thewheel tol'e'ave on stock due` to dellection or wear. Hence, tooth surf V.may be ground on theipinionwhich will notinterfere with the matingtoothsurfaces of the mate gear. VThis is but one use of the dressing mechanism ofthe present invention'. Otherv uses willimmef di'ately suggest themselves to those skilled in the art.

In the preferred construction of the present dressing mechanism, a pair of dressingtools are employed to permitrof dressing simultaneously opposite side surfaces of a grinding wheel. Each tool is mounted to swing in an arcuate path across the sidey surface tobe Vdressed and is adapted to be moved axiauy of its axis of swing during its arcuate movement, thereby to produce a modified shape' on the p'roles of the grinding wheel.

In the preferred construction, each tool is mounted on an arm that is secured to one end of an oscillatable shaft. A follower is secured to the opposite end of the shaft and the follower engages a` x'ed cam.' As the shaft is oscillated, then, to move the dressing tool across the wheel surface, the shaft is moved aiially, the extent and duration of its axial movement depending on the shapev of the control cam. Thus by selecting a camof suitable shape, any desired shape maybe dressed on theA grinding wheel.

In the drawings v Fig. 1 is a partY plan, part sectional view of a dressing apparatus built according to one embodiment of the invention for dressing the two sides of a grinding wheel simultaneously, and showing the dressing toolsl inV engagement with a wheel to be dressed;

Fig. 2 is a developed sectional Viewthrough the apparatus taken on the lin`e'2--2 of Fig. 1';

Fig. 3 is a developed View of a cam such as may be employed in this dressing apparatus for dressing a side surface of a grinding wheel'to have one pressure angle for part of its height and a lesser pressure angle for the remainder of its height;

Fig'. 4 is a view looking at the, backV end of one of the dressing mecl'ianisms'with` the protecting cover removed and showing particularly the fol'- lower 'and control cam of this' dressingY mechanism; and

Fig-5 is a diagrammatic View illustrating the operation ofthe dressing apparatus of the'present invention. l

In' the drawings, W denotesthe' grinding wheel whose side' surfaces are to be dressed. .lo denbtes') dressihgtol'for dressing the''lltside' sur# face of' this" wheel and Il'a dressingY tool for dressing the inside surface of the wheel. The dressing tool I is secured in any suitable manner in the free end of an arm I2 that is fastened at its opposite end to a shaft I4. 'I'he dressing tool II is mounted in any suitable manner in the free end of an arm I3 that is fastened at its opposite end to a shaft I5. The two arms I2 and I3 are suitably shaped so that the dressing tools carried thereby may be swung acrossthe inside and outside surfaces, respectively, of the grinding wheel without the arms interfering with one another.

The shafts I4 and I5 are mounted in a housing 20 with their axes inclined to one another at an angle approximating the included angle between the major parts of the: inside and outside surfaces of the grinding Wheel. Each shaft is mounted in the support 20 for both oscillatory and axial movement.

The oscillatory movements of the two shafts are produced by reciprocation of a piston 22 which moves in a cylinder 23 formed in the housing 20. This piston 22 has rack teeth 24 and 25 cut into it at opposite sides. 'Ihe rack teeth 24 mesh with the gear segment 26 which is clamped by means of a bolt 28 to the periphery of the shaft I4 at a point intermediate the ends of the shaft. The rack teeth 25 mesh with the spur gear segment 2l which is clamped by a bolt 29 to the shaft I intermediate the ends of that shaft. The piston 22 may be moved alternately in opposite directions to swing the dressing tools I and II back and forth across the side surfaces of the grinding wheel by any suitable means such as described, for instance, in the copending application of Ernest Wildhaber and Leonard O. Carlsen, Serial No. 304,150, led November 13, 1939.

Formed integral with the shaft I4 at'its rear end is an arm 30. The free end of this arm has its rear face formed to serve as a follower and this follower engages an arcuate face cam 32. This cam is xedly securedin an end plate 34 which is fastened in any suitable manner to the housing 20.

Integral with the shaft I5 is an arm 3|. The free end of this arm has its front face formed to act as a follower and this follower engages an arcuate face cam 33 which is secured by screws 34 (Fig. 4) to the housing 20.

The cams 32 and 33 may be of identical form. In Fig. 3, I have shown in development the form of cam which may be employed where it is desired to dress a grinding wheel so that each of its active side surfaces is of straight profile and one pressure anglefor'the greater portion of its height and of straight prole and smaller pressure angle for the remaining portion of its height. Such a wheel is shown in Figs. 1 and 5.

For dressing such a wheel, the control cam is formed with an arcuate projection 45 that is coaxial of the shaft I4 or I5 as the case may be, when the cam is in operative position, and that extends through an angle of 180 or less. The top land of this projection constitutes the control surface of thecam. In the case illus-A trated, the greater portion 46 of this control surface lies in a plane perpendicular to the axis of the shaft I4 or I5 with which the cam is associated, but a portion of the control surface, as denoted at 41, is slabbed off or inclined to the plane surface 46. While the free end of. arm 30 or arm 3|, as the case may be, is riding on the plane portion 46 of the corresponding1 control cam 32 or 33, during rotation of the associated shaft I4 or I5, the tip of the corresponding dressing tool I0 or Il simply swings in a plane perpendicular to the shaft I4 or I5. 'Ihus the tool I0 will dress the portion 40 of the profile of the outside active surface of the wheel, and the tool II will dress the portion 4I of the profile of the inside active surface of the wheel. When the free end of arm 30 or arm 3I rides on the inclined or slabbed off surface 4'I of the associated control cam, however, the corresponding shaft is y moved axially so that the associated tool I0 or II, as the case may be, dresses a surface on the wheel whose profile 42 or 43 is of less pressure angle than the profile 40 or 4I. Thus surfaces may be dressed on both the inside and outside of the wheel which are of one pressure angle for the greater part of their heights and of less pressure angle adjacent the tip of the wheel.

The free end of the arm 30 is held in engagement with the cam 32 by a coil spring 56 which is housed in a bore provided in the shaft I4. This spring is interposed between a nut 52 and the enlarged head 54 of a plunger 56. 'Ihe nut 52 threads into the bore of the shaft I4 `at the rear end of the shaft. The plunger 56 is mounted for sliding movement in the bore of the shaft I4 but is held against rotation relative thereto by a key 66 that slides in a slot formed in the periphery of the head 54 of the plunger. The plunger rod 56 projects rearwardly through an opening in the nut 52 and has a disc 58 secured to it by a pin 60. This disc seats against a shoulder formed on the rod 56 and is held against axial movement relative to the rod by a nut 62 which threads onto the rear end of the rod. A recess 12 is formed in the cap member 34 to receive the disc and nut and also to receive a disc 64 of brake or other frictional material. This disc 64 is secured in any suitable manner in the recess I2 and is adapted to engage the front face of the disc 58 to exert a slight frictional pressure on the plunger 56 and, through it, on the shaft I4, resisting turning of the shaft I4. Thus a light load is applied to the shaft to insure smooth, uniform rotational movement of the shaft as it is oscillated to move the diamond I0 across the outside surface of the grinding wheel. A cover plate 68 that is held to the cap member 34 by screws 'I0 serves to enclose the recess 'I2 in this cap member.

The free end of the arm 3| is held in-engage ment with the cam 33 by a coil spring 5I. This 'spring is mounted in a bore drilled in the shaft I5 and is interposed between one end of this bore and the enlarged head 53 of a plunger or rod 55. The plunger or rod 55 is mounted in the bore of the shaft I5 to be slidable therein but is secured to rotate therewith by a key 5'I which engages in a longitudinal slot formed in the head 53 of the plunger. The rear face of the head 53 of the plunger is adapted to seat against a disc 59 of suitable frictional material that is held in any suitable manner in a recess formed in a cover plate 6I. This cover plate is secured to the housing 26 by screws (not shown) which thread into the holes 63 (Fig. 4) tapped in the housing and it encloses the arm 3| and cam 33. The frictional disc 59 serves to put a light load on the plunger 55 and thereby on the shaft I5, to prevent vibration of the shaft I5 as it is oscillated to move the dressing tool I I across the inside surface of the grinding wheel.

The operation of the dressing mechanism of the present invention is illustrated in more detail but somewhat diagrammatically in Fig. 5, with reference to the dressing of the outside surface of a grinding wheel. The dressing tool I0, the shaft I4 which carries it, and the arm 30 which is connected to the shaft and which carries the follower, are shown in dotted lines in the positions which they occupy at one end of the movement of the dressing tool and in full lines in the positions which they occupy at the opposite end of the movement of the dressing tool. It will be seen that as the shaft I5 is rotated by movement of the piston 22, the follower will ride on the control surface of the cam 32. While the follower is in engagement with the plane portion 46 of this control surface, the point of dressing tool I I will travel in a plane parallel to the plane surface 46 and dress a surface on the grinding wheel whose prole 40 is perpendicular to the axis of the shaft I4 and inclined to the axis of the grinding wheel at an angle determined by the position of the axis of the shaft I4. As soon as the follower begins to ride up on the inclined portion 41 of the control surface of the cam, however, the shaft I4 is moved axially, moving the dressing tool axially and a surface is then dressed on the grinding wheel whose profile 42 is less inclined to the axis of the grinding wheel, that is, of smaller pressure angle than the prole 40.

It will be obvious that by making the portion 41 of the control surface of the cam curved at its juncture with the plane portion 46, the low angle portion of the grinding wheel profile can be made to blend into the high angle portion of the profile instead of these two portions being inclined at a sharp angle to one another as shown in the drawings. It will be obvious, also, that the proportions of the profile which are of large and small pressure angle, respectively, can be varied by varying the shape of the control surface of the cam. It will be further obvious that by suitably shaping the cam, any desired shape of profile can be produced on the grinding wheel.

While the invention has been described particularly in connection with a dressing mechanism for dressing rotary annular Wheels, it will be understood that it may be applied to the dressing of any form of grinding wheel. In general it may be said that the present application is intended to cover any variations, uses, or adaptations of the invention following the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. Dressing mechanism comprising a support, a shaft oscillatably and slidably mounted on said support, an arm secured to one end of said shaft, a dressing tool mounted in said arm, a second arm secured to the opposite end of the shaft, a cam and a follower, one of which is secured to the second arm and the other to said support, a

plunger mountedwithin the bore of said shaft to rotate with said shaft but to slide axially relative thereto, a coil spring interposed between the shaft and plunger to hold the follower resiliently in engagement with the cam, said plunger having an enlarged head at its rear end, means for swinging said shaft, and brake means engaging said head to apply a light frictional load on said shaft during its swinging movement.

2. Dressing mechanism comprising a support, a pair of shafts mounted in said support for rotary and axial sliding movement and having their axes inclined to one another at an angle equal approximately to the included angle between opposite sides of the wheel to be dressed, an arm secured to the front end of each of said shafts, a dressing tool mounted in one of said arms to engage one side surface of a grinding wheel and a dressing tool mounted in the other of said arms to engage the opposite side surface of said grinding wheel', a follower rigidly secured to the rear end of the shaft on which the rst named dressing tool is mounted, a face cam secured to said support between said follower and said arm and with which the follower is engaged, a follower rigidly secured to the rear end of the shaft on which the second named dressing tool is mounted, a face cam mounted at the rear of the latter follower to be engaged by the latter follower, each of said face cams being concentric of the shaft to which its cooperating follower is secured, means for resiliently holding the two followers in engagement with their respective cams, and a single means interposed between the two shafts for rotating the two shafts.

ARTHUR L. STEWART. 

